I. J. Hayes, C. B. Jones and J. E. Nicholls
Abstract:
This paper attempts to provide an understanding of the interesting
differences between two well-known specification languages. The main ideas
are presented in the form of a discussion. This was partly prompted by
Lakatos' book `Proof and Refutations' but since this paper is less
profound, characters from the childrens' television series `The Magic
Roundabout' are the speakers: Zebedee speaks for Z, Dougal puts the VDM
position, and Florence acts as the user. The specifications which are
presented have been made similar so as to afford comparison - in neither
the VDM nor the Z case would they be considered to be ideal presentations.
Some technical details are relegated to footnotes.